With the continuing demand for smaller feature sizes in the semiconductor industry, 193 nm optical lithography has emerged very recently as the technology to produce devices with sub-100 nm features. The use of such a shorter wavelength of light requires the bottom antireflective coating (BARC) to reduce the reflection on substrate and dampen the photoresist swing cure by absorbing light that has passed though the photoresist. Commercially available antireflective coatings consist of both organic and inorganic based materials. Typically, the inorganic ARC, which exhibits good etch resistance, is CVD based and is subject to all the integration disadvantage of extreme topography; on the other hand, the organic ARC materials are applied by spin-on process and have excellent fill and planarization properties, but suffer from poor etch selectivity to organic photoresists. As a result, a material that offers the combined advantages of organic and inorganic ARC is highly desired.
In this regards, we have recently discovered that certain phenyl-hydride based silsesquioxane resins exhibit excellent antireflective coating properties for 193 nm light. Although Bottom Anti Reflective Coatings (BARC) materials can effectively reduce the reflection of activating radiation, removal of BARC materials without damaging the overlying photoresist and/or the underlying substrate has been very challenging. The typical process to remove BARC is by a plasma etch process. Plasma etch often causes thinning of a photoresist layer. As a result, the patterns on the photoresist layer may be destroyed or becomes not transferable to the substrate layer. Plasma etch may also cause damage to the substrate thereby affecting the performance of the final device. What is more, the additional etch step for removing the BARC material increases cost and process complication in photolithographic practice.
Wet-etchable BARCs have been developed to address these issues. However, most of the wet-developable BARC materials are isotropic in nature, i.e, the entire layer of coating has an identical TMAH developing rate. This makes it difficult to obtain a vertical profile. As a result, anisotropically developing organic BARCs have been developed for 248 nm (KrF) and 193 nm (ArF) photolithography. These materials are initially insoluble in TMAH and become soluble after exposure to the wavelength of interest.
This invention pertains to switchable, wet-etchable antireflective coatings for photolithography produced from silsesquioxane resins. The antireflective coating (ARC) composition forms excellent spin-on film and are resistant to organic solvents, such as PGMEA, 2-heptonene, and TMAH, when cured at temperature 250° C. and below. With the addition of a photo-acid generator (PAG) to the ARC composition, the cured coating becomes soluble in developer solutions (TMAH) or stripper solutions (NE-89 and CCT-1) upon exposure to light through a photomask. The unexposed area of the ARC remains developer or stripper solution resistant. Secondly, when a thermo-acid generator (TAG) is added to the composition, the cured coating becomes developer-soluble (TMAH) upon exposure to the heat.